Table of Contents
一、中文版
给你一个以二进制形式表示的数字 s 。请你返回按下述规则将其减少到 1 所需要的步骤数：
- 如果当前数字为偶数，则将其除以 2 。
- 如果当前数字为奇数，则将其加上 1 。
题目保证你总是可以按上述规则将测试用例变为 1 。
示例 1：
输入： s = "1101"
输出： 6
解释： "1101" 表示十进制数 13 。
Step 1) 13 是奇数，加 1 得到 14
Step 2) 14 是偶数，除 2 得到 7
Step 3) 7 是奇数，加 1 得到 8
Step 4) 8 是偶数，除 2 得到 4
Step 5) 4 是偶数，除 2 得到 2
Step 6) 2 是偶数，除 2 得到 1
示例 2：
输入： s = "10"
输出： 1
解释： "10" 表示十进制数 2 。
Step 1) 2 是偶数，除 2 得到 1
示例 3：
输入： s = "1"
输出： 0
提示：
1 <= s.length <= 500s由字符'0'或'1'组成。s[0] == '1'
二、英文版
Given a number s in their binary representation. Return the number of steps to reduce it to 1 under the following rules:
- If the current number is even, you have to divide it by 2.
- If the current number is odd, you have to add 1 to it.
It's guaranteed that you can always reach to one for all testcases.
Example 1:
Input: s = "1101"
Output: 6
Explanation: "1101" corressponds to number 13 in their decimal representation.
Step 1) 13 is odd, add 1 and obtain 14.
Step 2) 14 is even, divide by 2 and obtain 7.
Step 3) 7 is odd, add 1 and obtain 8.
Step 4) 8 is even, divide by 2 and obtain 4.
Step 5) 4 is even, divide by 2 and obtain 2.
Step 6) 2 is even, divide by 2 and obtain 1.
Example 2:
Input: s = "10"
Output: 1
Explanation: "10" corressponds to number 2 in their decimal representation.
Step 1) 2 is even, divide by 2 and obtain 1.
Example 3:
Input: s = "1"
Output: 0
Constraints:
1 <= s.length <= 500sconsists of characters '0' or '1's[0] == '1'
三、My answer
class Solution:
def numSteps(self, s: str) -> int:
s_int = int(s,2)
ans = 0
while s_int != 1:
if s_int % 2 == 1:
s_int += 1
else:
s_int //= 2
ans += 1
return ans
四、解题报告
按照题意模拟即可。
注意：
s_int //= 2，不要写成 s_int /= 2，在例子 "1111011110000011100000110001011011110010111001010111110001" 报错。
可见虽然偶数时除以2，也明知道会整除，还是需要用 // 整除符号。
